1. Field of the Invention
The present invention relates to a water leakage monitoring system, which estimates leakage positions in water distribution blocks forming a water distribution pipeline network.
2. Description of the Related Art
Water purified by a public water treatment plant is supplied to a large number of customers spread over a large-area district via a water distribution pipeline network. Therefore, the water distribution pipeline network functions as an essential lifeline network to maintain customers' daily life. Thus, the distribution pipeline network has a need to constantly meet water demands for customers based on high reliability. If a breakage occurs in a part of a water distribution pipeline forming each water distribution block, the following problems arise. Namely, this is a factor of causing a disaster such as cave-in and submergence in the road. In addition, water leakage by crack and breakage of the pipeline is a factor of decreasing effective water (efficiency) with respect to the total distributed water. For this reason, it is desired to rapidly detect crack and breakage portions of the pipeline in addition to a decrease of a wall thickness of the pipeline as much as possible.
There is a conventional water leakage detection method generally employed. According to the method, a flow rate to each water distribution block is checked for a long term, and then, leakage is detected from a change of the flow rate. For example, the minimum nighttime flow rate of each water distribution block is measured at a nighttime zone when customers do not almost use water. Thereafter, a flow rate of the same time zone is checked. If there is a tendency for the flow rate to increase, it is determined that water leaks from any distribution pipeline forming the water distribution block.
When it is determined that water leaks, a workman must do the following work by using a water leakage detector. Specifically, the workman moves along a complex distribution pipeline including service pipe of customers in the water distribution block. The workman further detects an inflow sound using the water leakage detector at time zone when the water is not used, and thereby, estimates a water leakage portion of the pipeline.
Therefore, according to the foregoing water leakage detection method, the nighttime minimum inflow rate must be collected for a long period. For this reason, even if water now leaks from a certain portion in the distribution block, it may not be determined that water leaks so long as verification is made for a long time. As a result, a small crack of the water distribution pipeline is gradually made large as time elapses. Finally, the pipeline is broken; as a result, there is a possibility of causing a disaster such as cave-in and submergence in the road.
According to the foregoing conventional water leakage detection method, the following problem further arises. Specifically, even if it is determined that water leaks in a certain distribution block, it is impossible to estimate that water leaks from any distribution pipeline in the distribution block. As a result, a workman moves along the distribution pipelines forming the distribution block, and simultaneously, must strictly collect an inflow sound of the pipeline using the water leakage detector. Thus, this is a factor of increasing a workman's load, and effective water will be lost for a long term.
In recent years, some water leakage detection techniques have been proposed.
According to one conventional water leakage detection technique, an opening/closing lid of a water meter located on a service pipe led to customers from the distribution pipeline is provided with a sound detector. A specific sound detected by the detector from a body of the water meter is used to determine an occurrence of water leakage in the service pipe and to output the determined signal outside. (See FIG. 1 of Jpn. Pat. Appln. KOKAI Publication No. 2004-191139)
According to another conventional water leakage detection technique, the service pipe of customers led from the distribution pipeline is provided with a vibration detector and data storage means. The vibration detector measures a vibration level of a pipe caused by water stream flowing through the service pipe. The data storage means stores flow rate measurement data of water flow meter of the customer and the measured data from the vibration detector. Using the foregoing vibration detector and storage means, water leakage is detected from the vibration when water flows. (See FIG. 1 of Jpn. Pat. Appln. KOKAI Publication No. 2001-311676)